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- Landberg, Eva, et al.
(författare)
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Changes in the relative amounts of α2-3 and α2-6 linked sialic acid on free and protein-bound milk oligosaccharides during lactation
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Human milk contains large amounts of oligosaccharides, both in free and protein-bound forms. Sialic acid is a common constituent of milk oligosaccharides and is present α2-3 or α2-6 linked to galactose, α2-6 to N-acetyl glucosamine or α2-6 to N-acetyl galactosamine. High-performance anionexchange chromatography with pulsed amperometric detection (HPAEC-PAD) was used to quantify four major sialylated milk oligosaccharides. The concentrations of the individual oligosaccharides were analyzed in milk from five donors, followed separately during six to nine months of lactation. The oligosaccharides containing sialic acid a2-6 linked to galactose ( 6-sialyl lactose and LSTc) decreased more than tenfold during lactation. In contrast, the concentration of 3-sialyl lactose (3-SL) containing sialic acid a2-3 linked to galactose remained constant during nine months of lactation. Disialyl lacto-Ntetraose (DSLNT) which contain sialic acid linked α2-3 to Gal and α2-6 to GlcNAc decreased approximately threefold during lactation. Lectin ELISA was used to analyze sialic acid on the secreted milk glycoprotein bile-salt-stimulated lipase (BSSL ). There was a gradual decrease in the binding of Sambucus Nigra lectin to BSSL, indicating decreased amount of α2-6 linked sialic acid during lactation. In contrast, binding of Maackia Amurensis lectin remained constant, indicating a constant expression of α2-3 linked sialic acid on BSSL during lactation. This suggests a shift from preferentially 6-linked to 3-linked sialic acid on free and protein-bound oligosaccharides during lactation. The shift may reflect changes in sialyltransferase activities and, on a higher level, changes in the population of mammary epithelial cells. This finding may be of importance for the development of a correct immune response to environmental challenges.
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| 2. |
- Landberg, Eva, et al.
(författare)
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Quantitative changes of fucosylated human milk oligosaccharides during lactation in comparison to milk fucosyltransferase activity
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Human milk contains 7-20 g/L of free oligosaccharides. The oligosaccharides show large variations in size and structure. It has been suggested that milk oligosaccharides can prevent pathogenic microorganisms from attaching to the gastrointestinal epithelium by blocking bacterial adhesins. However, the biological role of milk oligosaccharides is far from understood. In this study, the major fucosylated oligosaccharides in milk were followed during six to nine months of lactation. Individual oligosaccharides were separated and quantified by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The fucosylated oligosaccharides 2-fucosyl lactose, lacto-N-fucopentaose I and lacto-N-di-fucohexaose I showed decreasing concentrations in milk during lactation. The concentrations of lacto-difucotetraose, lacto-N-fucopentaose II and Ill remained constant, while 3-fucosyl lactose (3-FL) showed increasing concentrations during lactation. The increase of 3-FL was found for all individuals independent of secretor status, but did not correlate to milk fucosyltransferase activity when the product 3-FL was measured separately. Instead all individuals showed a decrease in fucosyltransferase activity during lactation, indicating that fucosyltransferase activity in milk does not reflect the biosynthetic activity in the mammary gland. This study shows that the composition of fucosylated oligosaccharides vary considerably during the first six months of lactation. This may reflect unique biological roles of certain oligosaccharides in the infant's adaptation to the environment.
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